Roofing systems are typically incorporated into a structure in order to promote weather-tight integrity, and in particular, watertight integrity of the structure. So provided, a roofing system should allow a structure to shed water which is then typically guided to ground level and away from the base of the structure. Over the years, the roofing industry has adopted numerous roofing systems for use with various types of structures in an effort to provide lasting weather-tight integrity of the structure at an affordable cost.
Conventional roofing systems used with high-pitched roofs typically incorporate shingles which are formed of a variety of materials, including asphalt laden felt or fiberglass, cedar, or slate, among others. The shingles are commonly arranged in multiple rows or courses, with the shingles of each course being aligned in an end-to-end relationship and then mechanically fastened to a roof support structure. Successive courses are then arranged to partially overlay each previous course so that water will run down successive courses of shingles and off the roof without having the opportunity to flow underneath underlying courses of shingles and onto the underlying roof support structure. This roofing system becomes problematic, however, as the pitch of a roof is decreased. This is because water sheds more slowly from a low-pitched roof than from a high-pitched roof, therefore, providing a greater opportunity for any water contacting the exterior surfaces of the shingles to seep under the shingles and potentially damage the underlying roof support structure.
Due to the aforementioned problems, flat and other low-pitched roofs, such as those used in commercial buildings, have typically incorporated roofing systems with water impermeable membranes formed of alternating layers of bituminous compound and felt sheet material. The bituminous compound typically arrives at the job site in solid form and is then liquefied by commercial heaters. The liquid bituminous compound is then laboriously transported to the roof of the building and spread across the roof support structure, such as by mopping the liquid bituminous compound manually, until a substantially uniform layer is formed. The felt sheet material is then transported to the roof and laid upon the liquid bituminous layer, thereby bonding the felt to the roof support structure. This process is repeated several times until a liquid impermeable felt-bituminous membrane is formed. A layer of gravel is then typically formed above the membrane as a protective covering against wind and ultra-violet rays which both can damage the membrane.
In order to alleviate the labor intensive process of forming a felt-bituminous membrane upon a roof support structure, several roofing systems have been recently developed which incorporate liquid impermeable sheet materials which do not require the use of large quantities of liquefied bituminous compound or multiple layers of sheet material to form a watertight roof For example, U.S. Pat. Nos. 3,971,184 and 4,021,981 disclose insulated, water impermeable roofing systems, each of which incorporates factory assembled roofing panels.
As disclosed in the aforementioned patents, each roofing panel includes a self-adherent, water and vapor impermeable membrane upon which an insulation layer and an optional protective layer are constructed. The panels are adhered in a spaced-relationship about a roof support structure by removing a release paper from the impermeable membrane and then by pressing each panel against the support structure. Spaces between adjacent panels are then filled with a self-adherent plastic filler compound which bonds to the impermeable membranes of adjacent panels to form a continuous water and vapor impermeable layer which is formed at the bottom of the panels between the insulation layer and the roof support structure. Although these roofing systems have each met with a degree of commercial success, several problems limit their effectiveness, including: increased labor costs associated with preparing the roof support structure in order to promote adhesion of the liquid impermeable membrane to the support structure; the requirement for special equipment at the job site in order to apply the filler compound, and; the expense of the filler compound itself.
Additionally, U.S. Pat. No. 4,783,942 discloses a roofing system incorporating fiberglass faced mineral boards which are mechanically fastened to a roof support structure of corrugated material. A layer of adhesive is applied to the upper faces of the mineral boards and then rolls of waterproof sheet material, such as ethylene propylene diene terpolymer (EPDM), are arranged on and bonded to the adhesive layer. Although this roofing system has also met with a degree of commercial success, several problems limit its effectiveness, including the labor intensive job site application of the EPDM to the mineral boards, and the added time and care which must be used by the installers to ensure that the entire roof support structure is properly covered by overlapping sheets of the EPDM.
Therefore, it would be desirable to provide a roofing system which incorporates a series of individual roofing panels each of which incorporates a liquid impermeable membrane and each of which can be installed by unskilled laborers in a relatively short period of time to form a watertight roofing system upon a variety of roof support structures.